I'm beginning to get the impression that writing about Trader Joe's is some sort of fall-back for food writers who don't have any other good ideas. On the surface, this seems like a good idea. There are plenty of good things to say about it and they come out with new things frequently, most of which are worth a mention. Unfortunately, the new things - products, store locations, etc - aren't what seem to attract the press. They seem to enjoy writing about how they are or are not impressed with the store and why it is popular.
Here is yet another article from an east coast paper where the author wondered why Trader Joe's was so popular, tried it and decided that it was a store worth visiting, at least from time to time. The problem with the piece is that the Washington DC area already has several Trader Joe's locations, so the chance that this revelation is actually news to residents, or to anyone else who has shopped at Trader Joe's, is slight.
You don't really see articles in this same vein for other grocery stores. No one visits Safeways and comments on the employee uniforms ("what was with the staff in the retro Hawaiian shirts?"), so the problem must be hype. Every time a new store opens, a buzz arises from that city about the store and the wonders that residents will have access to. The buzz spreads outward and soon other cities - even those that have had the stores for a decade - start talking about it. Again.
By all means, continue to write about the store, but at least make sure that there is something new to write about - a new store, a new product, etc. - when you do it.